Image forming apparatus to acquire image bearing member surface potentials

Abstract

In an image forming apparatus, a control unit performs a control to cause an exposing unit to expose a plurality of image bearing members at different times to form exposure regions on the plurality of image bearing members, to acquire results acquired by applying direct current voltage lower than discharge start voltage to a plurality of abutting members by an applying unit when the exposure regions pass by abutting parts against the abutting members and detected by a detecting unit, and to, based on the acquired results of the detections, acquire information regarding the surface potentials of the plurality of image bearing members.

What is claimed is: 
     
       1. An image forming apparatus comprising:
 a first image forming unit including a rotatable first image bearing member, a first charging member configured to come into contact with the first image bearing member to form a first charging portion and to charge a surface of the first image bearing member at the first charging portion, and a first development member configured to supply a developer to the surface of the first image bearing member; 
 a second image forming unit including a rotatable second image bearing member, a second charging member configured to come into contact with the second image bearing member to form a second charging portion and to charge a surface of the second image bearing member at the second charging portion, and a second development member configured to supply a developer to the surface of the second image bearing member; 
 an exposing unit configured to expose the surface of the first image bearing member charged by the first charging member and the surface of the second image bearing member charged by the second charging member; 
 a charging voltage applying unit configured to apply charging voltage to the first charging member and the second charging member; 
 a detecting unit configured to detect a first current value of electric current flowing from the first charging member to the first image bearing member at the first charging portion and a second current value of electric current flowing from the second charging member to the second image bearing member at the second charging portion while the charging voltage is applied; and 
 a control unit configured to control the charging voltage applying unit and the exposing unit, 
 wherein in a case where the detecting unit detects the first current value and the second current value, the control unit is configured to perform control so that timing when the surface of the first image bearing member exposed by the exposing unit reaches the first charging portion is different from timing when the surface of the second image bearing member exposed by the exposing unit reaches the second charging portion while the charging voltage applying unit applies the charging voltage having an absolute value smaller than an absolute value of discharge start voltage. 
 
     
     
       2. The image forming apparatus according to  claim 1 ,
 wherein the charging voltage applying unit has separate power supplies each configured to apply voltage to corresponding one of the first charging member and the second charging member. 
 
     
     
       3. The image forming apparatus according to  claim 1 , wherein the charging voltage applying unit has a common power supply configured to apply voltage to the first charging member and the second charging member. 
     
     
       4. The image forming apparatus according to  claim 1 ,
 wherein in a case where the detecting unit detects the first current value and the second current value, the control unit is configured to control the exposing unit to expose the first image bearing member and the second image bearing member so that an absolute value of a surface potential formed on the first image bearing member and an absolute value of a surface potential formed on the second image bearing member are small after the control unit controls the charging voltage applying unit to apply direct current voltage smaller than the discharge start voltage to the first charging member and the second charging member, while the absolute value of the surface potential of the first image bearing member and the absolute value of the surface potential of the second image bearing member are equal to or smaller than a predetermined value. 
 
     
     
       5. The image forming apparatus according to  claim 4 ,
 wherein the predetermined value is equal to substantially 0 V. 
 
     
     
       6. The image forming apparatus according to  claim 1 ,
 wherein in a case where the detecting unit detects the first current value and the second current value, the control unit is configured to control the exposing unit to expose the first image bearing member and the second image bearing member so that an absolute value of a surface potential formed on the first image bearing member and an absolute value of a surface potential formed on the second image bearing member are small after the control unit controls the charging voltage applying unit to apply direct current voltage equal to or larger than the discharge start voltage to the first charging member and the second charging member. 
 
     
     
       7. The image forming apparatus according to  claim 1 ,
 wherein the control unit is configured to control the first image bearing member and the second image bearing member to execute an operation to reduce an influence of a discharge product attached to surfaces of the first and second image bearing members based on the first current value and the second current value detected by the detecting unit. 
 
     
     
       8. The image forming apparatus according to  claim 7 ,
 wherein, in a case where the absolute value of electric current value or voltage value detected by the detecting unit when the surface of the first image bearing member exposed by the exposing unit passes by the first charging portion is equal to or greater than a predetermined threshold value, the control unit causes the first image bearing member to execute the operation, and 
 in a case where the absolute value of the electric current value or voltage value detected by the detecting unit when the surface of the second image bearing member exposed by the exposing unit passes by the second charging portion is equal to or greater than a predetermined threshold value, the control unit causes the second image bearing member to execute the operation. 
 
     
     
       9. The image forming apparatus according to  claim 1 ,
 wherein the surface of the first image bearing member exposed by the exposing unit and the surface of the second image bearing member exposed by the exposing unit are formed in an entire region exposable by the exposing unit in a direction substantially orthogonal to a movement direction of the surfaces of the first image bearing member and the second image bearing member. 
 
     
     
       10. The image forming apparatus according to  claim 1 , wherein a developer remaining on the surfaces of the first image bearing member and the second image bearing member without being transferred onto a transfer material after images formed with the developer are transferred from the first image bearing member and the second image bearing member to the transfer material is collected by the first development member and the second development member configured to supply the developer to the surfaces of the first image bearing member and the second image bearing member. 
     
     
       11. The image forming apparatus according to  claim 10 , wherein the developer is a one-component developer. 
     
     
       12. An image forming apparatus comprising:
 a first image forming unit including a rotatable first image bearing member, a first charging member configured to come into contact with the first image bearing member to form a first charging portion and to charge a surface of the first image bearing member at the first charging portion, a first development member configured to supply a developer to the surface of the first image bearing member, and a first transfer member configured to transfer an image formed with a developer on a surface of the first image bearing member to a transfer material at a first transfer portion; 
 a second image forming unit including a rotatable second image bearing member, a second charging member configured to come into contact with the second image bearing member to form a second charging portion and to charge a surface of the second image bearing member at the second charging portion, a second development member configured to supply a developer to the surface of the second image bearing member, and a second transfer member configured to transfer an image formed with a developer on a surface of the second image bearing member to a transfer material at a second transfer portion; 
 an exposing unit configured to expose the surface of the first image bearing member charged by the first charging member and the surface of the second image bearing member charged by the second charging member; 
 a transfer voltage applying unit configured to apply transfer voltage to the first transfer member and the second transfer member; 
 a detecting unit configured to detect a first current value of electric current flowing from the first transfer member to the first image bearing member and a second current value of electric current flowing from the second transfer member to the second image bearing member while the transfer voltage is applied; and 
 a control unit configured to control the transfer voltage applying unit and the exposing unit, 
 wherein in a case where the detecting unit detects the first current value and the second current value, the control unit is configured to perform control so that timing when the surface of the first image bearing member exposed by the exposing unit reaches the first transfer portion is different from timing when the surface of the second image bearing member exposed by the exposing unit reaches the second transfer portion while the transfer voltage applying unit applies the transfer voltage having an absolute value smaller than an absolute value of discharge start voltage. 
 
     
     
       13. The image forming apparatus according to  claim 12 , wherein in a case where the detecting unit detects the first current value and the second current value, the control unit is configured to control the exposing unit to expose the first image bearing member and the second image bearing member so that an absolute value of a surface potential formed on the first image bearing member and an absolute value of a surface potential formed on the second image bearing member are small after the control unit controls the transfer voltage applying unit to apply direct current voltage smaller than the discharge start voltage to the first transfer member and the second transfer member, while the absolute value of the surface potential of the first image bearing member and the absolute value of the surface potential of the second image bearing member are equal to or smaller than a predetermined value. 
     
     
       14. The image forming apparatus according to  claim 13 ,
 wherein the predetermined value is equal to substantially 0 V. 
 
     
     
       15. The image forming apparatus according to  claim 12 , in a case where the detecting unit detects the first current value and the second current value, the control unit is configured to control the exposing unit to expose the first image bearing member and the second image bearing member so that an absolute value of a surface potential formed on the first image bearing member and an absolute value of a surface potential formed on the second image bearing member are small after the control unit controls the transfer voltage applying unit to apply direct current voltage equal to or larger than the discharge start voltage to the first transfer member and the second transfer member. 
     
     
       16. The image forming apparatus according to  claim 12 , the control unit is configured to control the first image bearing member and the second image bearing member to execute an operation to reduce an influence of a discharge product attached to surfaces of the first and second image bearing members based on the first current value and the second current value detected by the detecting unit. 
     
     
       17. The image forming apparatus according to  claim 16 ,
 wherein, in a case where the absolute value of electric current value or voltage value detected by the detecting unit when the surface of the first image bearing member exposed by the exposing unit passes by the first transfer portion is equal to or greater than a predetermined threshold value, the control unit causes the first image bearing member to execute the operation, and 
 in a case where the absolute value of electric current value or voltage value detected by the detecting unit when the surface of the second image bearing member exposed by the exposing unit passes by the second transfer portion is equal to or greater than a predetermined threshold value, the control unit causes the second image bearing member to execute the operation. 
 
     
     
       18. The image forming apparatus according to  claim 12 ,
 wherein the surface of the first image bearing member exposed by the exposing unit and the surface of the second image bearing member exposed by the exposing unit are formed in an entire region exposable by the exposing unit in a direction substantially orthogonal to a movement direction of the surfaces of the first image bearing member and the second image bearing member. 
 
     
     
       19. The image forming apparatus according to  claim 12 , wherein a developer remaining on the surfaces of the first image bearing member and the second image bearing member without being transferred onto a transfer material after images formed with the developer are transferred from the first image bearing member and the second image bearing member to the transfer material is collected by the first development member and the second development member configured to supply the developer to the surfaces of the first image bearing member and the second image bearing member. 
     
     
       20. The image forming apparatus according to  claim 19 , wherein the developer is a one-component developer.